1. Field of the Invention
This invention relates to a hard coat film to be provided on a surface of a window, a display, and the like. Particularly, this invention relates to the hard coat film to be provided on a surface of a display such as a liquid crystal display (LCD), a CRT display, an organic electroluminescence display (ELD), a plasma display (PDP), a surface-conduction electron-emitter display (SED), and a field emission display (FED).
2. Description of the Related Art
A hard coat layer as a protection film is often provided on a surface of an optical component member of a display medium such as a liquid crystal display. Further, a function layer is often provided on the hard coat layer. Examples of the function layer to be provided on the hard coat layer include an anti-reflection layer for preventing reflection of light and the like.
In the case of providing the function layer on the hard coat layer, when adhesion between the hard coat layer and the function layer (hereinafter, adhesion means the adhesion between a hard coat layer and a function layer) is insufficient, scratches are easily caused on the hard coat layer or the function layer due to peeling caused by an impact applied on a surface of the function layer. Also, as a result of a weather resistance test, it has been found that the function layer or the hard coat layer is not only deteriorated by ultraviolet ray irradiation but also bonding at a boundary is weakened to further diminish the adhesion. Accordingly, scratches are more easily caused on the hard coat layer or the function layer, and there is a fear that the function layer is peeled off to make the product unusable.
Therefore, studies on improvement in adhesion have been conducted, and, for example, Patent Document 1 (JP-A-2001-287308) discloses that excellent adhesion to a function coating is achieved when a hard coat layer has a surface hardness (pencil hardness) of 2H or more, a surface shaving index of 1.0 to 15.0, and a centerline average surface roughness (Ra) on a surface of the hard coat coating of 0.001 to 0.02 μm.
For example, it is described in Patent Document 1 (JP-A-2001-287308) that a value of the surface shaving index is a parameter indicating a precipitation of a filler contained in the hard coat coating, and that a shaved white powder adheres to the film surface to transfer to the function layer laminated on the hard coat layer, etc. when the surface shaving index largely deviates from the above-specified range, thereby causing a reduction in adhesion. Also, it is described that, when the average surface roughness (Ra) exceeds the above-specified upper limit, the adhesion is undesirably diminished in the case where the function coating is laminated.
However, the degree of precipitation of filler is not the sole parameter that influences on the adhesion between the hard coat layer and the function layer. Also, according to findings of the inventors of this invention, excellent adhesion has been achieved when the centerline average surface roughness of the above-mentioned hard coat layer surface is out of the range specified in Patent Document 1. Accordingly, it is difficult to allege that there is correlativity between the adhesion and the hard coat coating centerline average surface roughness, and it is not appropriate to specify the hard coat coating centerline average surface roughness for the purpose of obtaining a hard coat coating increased in adhesion. Also, since accuracy of the method of measuring the surface shaving index is insufficient, the surface shaving index is not appropriate as the parameter for evaluating characteristics of hard coat coating.    Patent Document 1: JP-A-2001-287308